<template>
  <div id="app">
    <router-view/>
  </div>
</template>
<script>
export default {
  name: 'App',
  data () {
    return {
      user: JSON.parse(sessionStorage.getItem('user'))
    }
  },
  created () {
    // 在页面加载时读取sessionStorage里的状态信息
    if (sessionStorage.getItem('store')) {
      this.$store.replaceState(
        Object.assign(
          {},
          this.$store.state,
          JSON.parse(sessionStorage.getItem('store'))
        )
      )
    }
    // 在页面刷新时将vuex里的信息保存到sessionStorage里
    // beforeunload事件在页面刷新时先触发
    window.addEventListener('beforeunload', () => {
      sessionStorage.setItem('store', JSON.stringify(this.$store.state))
    })
  },
  watch: {
    '$store.state.menu': {
      handler (val, old) {
        console.log('进入app')
        console.log(val)
        console.log('=====')
        console.log(old)
        if (old && this.user != null) {
          this.$store.commit('setRouter', val)
        }
      },
      immediate: true
    }
  }

}
</script>

<style>
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
}

nav {
  padding: 30px;
}

nav a {
  font-weight: bold;
  color: #2c3e50;
}

nav a.router-link-exact-active {
  color: #42b983;
}
</style>
